Silver pastes are commonly used to form electrical connections with metal conductive layers. See, for example, application Ser. Nos. 10/956,371; 12/458,071; and 12/458,111, and U.S. Pat. No. 4,941,929, which references describe example silver frits/pastes and are hereby incorporated by reference herein in their entireties. Such silver pastes may be useful in connection with a wide variety of applications including, for example, refrigerator and/or freezer doors, oven doors, vehicle windshields, photovoltaic devices, plasma display panels (PDPs) and other electronic devices, and/or the like.
The silver paste typically is made to penetrate the top layer (or layers) of oxidized or ceramic films so as to come into contact with a metallic conductive layer(s). Unfortunately, however, silver pastes are not always able to penetrate the topmost layer (or layers) of all thin film coatings to reach the metallic conductive layer(s), particularly in cases where the layer (or layers) provided over the metallic conductive layer(s) are very strong dielectrics. For instance, when the design of the coating stack includes top layers of transitional elements or compounds including, for example, Zirconium, Scandium, Titanium, Vanadium, Yttrium, Niobium, Lanthanum, Hafnium, and/or Tantalum, highly dielectric films with high surface strengths may be created. Standard silver pastes commercially used in the market today often will not penetrate these highly dielectric films and thus will not create an electrical contact to the metal current-transmitting layers within the coating stack design.
A side-by-side comparison was performed by applying Ag-based bus bars on a PPII HT coating with and without a ZrO2 overcoat. Samples with the ZrO2 overcoat generated arcing and hot spots at low powers, whereas samples with no ZrO2 overcoat produced good results and were capable of carrying “standard” power levels (e.g., 24 VAC for a 5 ohm coating) for a long period of time without breaking down. In this case the glass temperature was reported to be about 150 degrees F.
In part because of the poor or non-existent connection formed between the silver paste and the conductive layers (which causes a higher electrical resistance), a higher voltage must be provided. Unfortunately, however, providing a higher voltage may result in excess or otherwise undesirable localized heating at the contact interface and sometimes even in “blowout or electrical leakage” of the connection. The high voltages that cause these problems may be provided intentionally or during voltage surges, but the blowout problem may be common to both situations.
Thus, it will be appreciated that there is a need in the art for an improved frit paste that is capable of making an electrical connection with at least one conductive layer in a layer stack, even where the at least one conductive layer is protected by one or more strong dielectric layers, and/or methods of making the same. It also will be appreciated that there is a need in the art for an improved frit paste that is capable of surviving voltage surges.
One aspect of certain example embodiments relates to a chemically modified silver paste that is capable of forming an electrical connection with at least one conductive layer in a layer stack, even where the at least one conductive layer is protected by one or more strong dielectric layers (such as, for example, Zirconium or the like).
Another aspect of certain example embodiments relates to a chemically modified silver paste that includes tin fluoride. In certain example embodiments, the tin fluoride concentration or amount is less than 10.0% by weight, more preferably between 0.2-6.0% by weight.
Still another aspect of certain example embodiments relates to a silver paste that is capable of surviving voltage surges.
Yet another aspect of certain example embodiments relates to a silver paste that involves forming an electrical connection with at least one conductive layer in a layer stack, even where the at least one conductive layer is protected by one or more strong dielectric layers, without needing to equipment or processing changes to the normal manufacturing process in place at fabricators worldwide.
In certain example embodiments of this invention, a method of making a product comprising a coating supported by a glass substrate is provided. The substrate supporting the coating is provided, with the coating comprising a plurality of thin film layers including at least one dielectric layer and at least one conductive layer located between the at least one dielectric layer and the substrate. A silver paste is provided on the coating, with the silver paste being at least initially fluorinated. At least the fluorinated silver paste is heated. An electrical connection is formed between the at least one conductive layer and the silver paste. According to certain example embodiments, the product may be an electronic device; refrigerator, freezer, or oven door; vehicle windshield; etc.
In certain example embodiments of this invention, a method of making a fluorinated silver paste is provided. A silver paste is provided. Tin fluoride is added to the silver paste. The amount of tin fluoride in the fluorinated silver paste is less than 10% by weight. The concentration of fluorine in the tin fluoride is less than 1%.
In certain example embodiments of this invention, a fluorinated silver paste is provided. The fluorinated silver paste comprises a silver paste and tin fluoride. The amount of tin fluoride in the fluorinated silver paste is less than 10% by weight, the concentration of fluorine in the tin fluoride is less than 1%, and a temperature required for baking the fluorinated silver paste is substantially the same as the temperature would be for the initially provided silver paste.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.